[LLDB] Add per-thread register infos shared pointer in gdb-remote

In gdb-remote process we have register infos defind as a refernce object of
GDBRemoteDynamicRegisterInfo class. In past register infos have remained
constant througout the life time of a process.

This has changed after AArch64 SVE support where register infos will have
per-thread configuration. SVE registers will have per-thread size and can
be updated while running. This patch aims to build up for that support by
changing GDBRemoteDynamicRegisterInfo reference to a shared pointer deinfed
per-thread.

Reviewed By: labath

Differential Revision: https://reviews.llvm.org/D82857